Turbine bucket wheel



Filed y 19. 1954 2 Sheets-Sh 1 Invent w. R n

His Att? neH w e r d n A A. w. RANKIN TURBINE BUCKET WHEEL July 22, 19582' Sheets-Sheet 2 Filed May 19. 1954 Inventor Andrew W. Ran k i T: 1:35g

H is Attorne y United States Patent 2,844,355 TURBINE BUCKET WHEELAndrew W. Rankin, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York Application May 19, 1954, Serial No.430,814 3 Claims. (cr. 253-71 In the usual arrangement of this kind, thecircumferential shoulder portions least at one location of the dovetailrim are cut away at defining a notch opening through which the bucketsare inserted radially and slid circumferentially along the rim duringassembly.

The buckets are held in place on the rim by a notch closing meansusually consisting of a notch bucket comprising a base and bladeportion, or a notch block. The notch closing means also serves to fillout the contour of the wheel.

When the centrifugal forces acting on the bucket wheel are not verylarge relative to the high-temperature strength of the materials usedfor buckets and rotors, a notch bucket or solid notch block in the notchopening proves very satisfactory. However, in modern high-temperatureturbines it is no longer possible to employ a notch bucket or heavynotch block because of the reduced strength of the materials at hightemperatures. Accordingly, a heavy notch closing means results in anundesirable encroachment on design margins and safetyfactors. Inaddition, the heavier notch closing means requires that pins or rivetsbe driven through the wheel rim to aid in holding the notch block orbucket on the bucket wheel. This type of connection weakens the diskmember in those areas containing the rivet or pin holes and theresulting stress concentrations introduce the possibility of cracksdeveloping in the highly stressed areas around the holes through thewheel. If such cracking should develop, the entire wheel or rotor mustbe replaced or suitably modified to eliminate the cracked regions.

Accordingly, an object of this invention is to provide an improvednotch-block arrangement for high-speed hightemperature turbinespermitting a reduction in weight and resulting stresses in the bucketwheel rim at the place where the notch closing means is installed.

A further object is to provide a notch block assembly of utmostsimplicity which can be quickly and easily locked in place in the bucketwheel, and which may readily be removed when it becomes necessary torepair or replace buckets.

A still further object is to lock the notch closing means to the bucketwheel without having to drill any holes through the wheel rim.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings, in whichFig. 1 illustrates an adjacent the notch 19, 20 and recess 18. Thelength ured in an axial direction relative 2,844,355 Patented July 22,1958 ICC exploded perspective of a bucket wheel portion embodying theinvention; Fig. 2 is a side view of a portion of a bucketed wheelshowing the notch block assembly installed on the wheel; Fig. 3 is asectional view taken along lines 33 of Fig. 2, and Fig. '4 is amodification of the lower notch block member.

Generally stated, the invention is practiced by providing a lightweightthree-piece notch block assembly in the notch opening in the bucketwheel to prevent relative movementbetween the buckets and to lock themin place.

Referring first to Fig. 1, there is shown a perspective view of a diskmember 1 having a grooved rim portion defining a dovetail 2. Thedovetail of the rim forms shoulders 3, 4, 5, 6. These shoulders are cutaway for a distance slightly greater than the dovetail thickness ofbucket 8 to form notch opening 7. Bucket 8, comprises blade 9 and baseportion 10, which latter defines a conjugate dovetailgroove 11 of thesame configuration as the rim dovetail 2. The thickness of the bucketdovetail is measured parallel to the circumference of disk member 1.

Referring now more particularly to Figs. 2 and 3, the notch opening isshown as being filled by a notch block assembly including members 15, 16and 17. The upper notch member 15 defines a fork member comprising legsof member 15 measto the disk member 1 is substantially less than theaxial width of the bucket dovetails adjacent the notch opening, whilethe width of member 15 measured in a circumferential direction relativeto the disk member 1 is substantially equal to the circumferential widthof the notch opening'i. The width of the bucket dovetail is measuredparallel to the axis of disk member 1. The notch block member 15 wheninserted into the notch opening straddles the rim 1a of the disk member1 and fills part of the cut-away portions of shoulders 4 and 6. Theupper axially extending side surfaces of member 15 contacts the sides ofthe base portion of the adjacent buckets at substantially the topthereof.

The member 15 is locked in place in the bucket wheel by key meansbetween the member 15 and the buckets opening. The locking means betweenthe notch member 15 and each of the buckets adjacent the notch openingbeing identical, only the locking means between member 15 and one of theadjacent buckets will be described here. The key means consists ofcooperating recesses 12 and 21 in the base portion 10 of bucket 8adjacent the notch opening and the notch block member 15 respectively,and key 24 for insertion into said recesses. The cooperating recesses 12and 21 are located in a radial direction beyond the rim 1a of the diskmember, and runs in a direction substantially perpendicular to the faceof the disk member and parallel to theaxis thereof.

The buckets disposed on the bucket Wheel are sometimes subjected totangential vibration, and to restrain the buckets adjacent the notchopening against tangential movement relative to the disk member it isrequired to locate in the notch opening adjacent the base of thedovetail additional supporting means for the buckets. In accordance withthe present invention, the additional supporting means for the bucketsadjacent the notch opening comprise notch blocks 16, 17, inserted in thedisk member at the base of the dovetail.

Since the notch block members 16, 17 are identical in shape, location,and installation, only one has reference numerals applied thereto. Inthe preferred embodiment as shown in Figs. 2 and 3, the notch member 16is rectangular in shape and located in a circumferential groove 22defined by the disk member.

The axial and circumferential dimensions of member 16 are substantiallyequal to the axial width of groove 22 and circumferential dimension ofnotch opening 7 respec itvely. The radial dimension of member 16 issubstantially equal to the distance between the bottom of groove 22 andthe under surface of shoulder 3. For ease of assembly, however, theaxial length of the lower notch member above the groove 22 may beincreased, as disclosed at 16a in Fig. 4, so that its outer face matchesthe face of the wheel rim.

Notch block member 16 is locked in placein the notch opening 7 by keymeans similar to that used to lock member 15 to the bucket wheel. Thekey mean for locking the member 16 to the buckets 8, 13 adjacent thenotch opening being the same only the locking means between member 16and one of the adjacent buckets will be described. The key meanscomprises cooperating recesses 14, 23 in the bucket base 10 and notchblock 16 respectively and key 25 for insertion into the cooperatingrecesses 14, 23 to lock the bucket 8 and notch block against movementrelative to each other.

It will be realized by those skilled in the art that radial displacementof the notch block assembly is prevented by the key means abovedescribed locking the assembly to the buckets 8, 13 adjacent the notchopening 7, and axial displacement of the assembly is prevented by theinterengagement between the disk membe 1 and notch block members 15, 16and 17 respectively. The keys are retained against axial displacementrelative to the bucket wheel by peening the buckets 8, 13 and the notchclosing members over the ends of the keys as illustrated at 26.

The bucket wheel is assembled in the following manner:

The buckets 8 are inserted radially through the notch opening 7 and slidto the left or right along the rim of disk member 1. After all thebuckets are located on the wheel, the notch opening is then closed bythe notch block assembly embodying my invention. The two lower notchblocks 16, 17 are inserted radially into the grooves 22 defined by thedisk member 1 at the base of the dovetail. These blocks are then lockedto the' buckets 8, 13 adjacent the notch opening by inserting the keys25. The key assembly may be constructed closing means is inserted in thebucket wheel as, for instance, by drilling the cooperating recesses 14,23 as one hole and then inserting the dowel pins 25. Then the uppernotch piece is inserted in the notch opening with the legs 19,straddling the rim portion-1a which fits into recess 18. The member 15is then locked to the buckets adjacent the notch opening by adding thekeys 24, which are located radially outward beyond the rim 1a of thedisk member 1.

The keys are then fixed in portion of the buckets 8, 13 over the ends ofthe keys.

Thus it will be seen that the invention provides a lightweight notchopening filling means requiring no holes in the highly-stressed diskmember, and which can be quickly and easily installed in the bucketwheel, and readily removed by drilling away the peened-over portionswhen it is necessary to repair or replace buckets.

While two. embodiments of the invention have been described in detailherein, it will be obvious to those skilled in the art that changes andsubstitutions of equivalents might be made. For example, the notch blockassembly may be attached to the adjacent buckets by grub screws or othermechanical equivalents of the dowel pins 24. In addition this inventionis also applicable to dovetails having either a greater or lesser numberof shoulders. It is, of course, desired to cover by the appended claimsall such modifications as fall within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A turbo-machine bucket-wheel assembly comprising a disk member havingan imperforate rim portion defining a circumferential dovetail, and acircumferential groove at the base of the dovetail on either sidethereof, a rowof buckets each having a base defining a conjugatedovetail groove adapted to engage the rim dovetail, the

place by peening an adjacent and the notch block members after the notchrim also defining at least one notch opening extending radially acrossthe rim portion defining the dovetail through which the buckets areinserted during assembly, and means located between buckets disposedadjacent the notch opening for closing the notch opening to preventrelative movement between the disk member and the buckets, said meansincluding a fork member having legs disposed in the notch opening, apair of similar rectangular members disposed in the portion of thecircumferential grooves in radial alignment with the notch opening, thecircumferential dimension of said fork and rectangular members beingsubstantially equal to that of the notch opening, and cooperatingaxially extending key means interengaging the fork and rectangularmembers with the buckets adjacent the notch opening to prevent radialdisplacement of the fork and rectangular members relative to the diskmember, the cooperating key means between the fork member and theadjacent buckets being disposed at a location radially beyond theimperforate rim of the disk member.

2. A high speed turbo-machine bucket-wheel assembly comprising a diskmember having an imperforate rim portion defining a circumferentialdovetail, and a circumferential groove at the base of the dovetail oneither side thereof, a row of buckets each having a base defining aconjugate dovetail groove adapted to engage the rim dovetail, the rimalso defining at least one notch opening extending radially across therim portion defining the dovetail through which the bucket dovetails areinserted during assembly, and meanslocated between buckets disposedadjacent the notch opening for closing the notch opening to preventrelative movement between the disk member and the buckets, said meansincluding a fork member having legs disposed in the radially outerportions of the notch opening, a pair of similar generally rectangularmembers disposed in the portion of the circumferential grooves radiallyaligned with the notch opening, the circumferential dimension of thefork and rectangular members being substantially equal to that of thenotch opening, the axial dimension of the fork member being no greaterthan the width of the dovetail bases of the buckets adjacent the notchopening, the axial dimension of said rectangular members beingsubstantially equal to that of said grooves, and cooperating axiallyextending key means interengaging the fork and rectangular members withthe buckets adjacent the notch opening to prevent radial displacement ofthe fork and rectangular members relative to the disk member, thecooperating key means between the fork member and theadjacent bucketsbeing disposed at a location radially beyond the imperforate rim of thedisk member.

tion defining a circumferential dovetail, and a circumferential grooveat the base of the dovetail on either side thereof, a row of bucketseach having a base defining a conjugate dovetail groove adapted toengage the rim dovetail, the rim also defining at least one notchopening extending radially across the rim portion defining the dovetailthrough which the bucket dovetails are inserted during assembly, andmeans located between buckets disposed adjacent the notch opening forclosing the notch opening to prevent relative movement between the diskmember and the buckets, said means including a fork memher having legsdisposed in the radially outer portions of the notch opening, a pair ofL-shaped members one leg of which is disposed in the portion of thecircumferential grooves in radial alignment with the notch opening, thecircumferential dimension of the fork and L- shaped members beingsubstantially equal to that of the notch opening, the axial dimension ofthe fork member being no greater than the width of the dovetail bases ofthe buckets adjacent the notch opening, the axial dimen sion of the legof said L-shaped member disposed in the groove and that of the other legof said L-shaped memher being substantially equal to the width of thegroove and the distance from the inside of the groove to the side of thedisk member respectively, and cooperating axially extending key meansinterengaging L-shaped members with the buckets adjacent the notchopening to prevent radial displacement of the fork and L-shaped membersrelative to the disk member, the cooperating key means between the forkmember and the adjacent buckets comprising dowel pins engaging axialrecesses in abutting portions of the fork member and bucket and locatedradially beyond the imperforate rim the fork and I of the disk member,whereby the highly stressed disk rim is not weakened by the key means.

References Cited in the file of this patent UNITED STATES PATENTS

